is there a ghost in my machine?

Hi, all, I've been reviving a vintage stereo setup and can't seem to isolate the problem with the right channel speakers; the right channel fades out and dies completely but only under certain circumstances.
 Here are the details:  I've got a just-renovated Linn LP12, and a Conrad-Johnson PV1 which just came back from getting its tubes checked and pots cleaned (because I wasn't getting sound in the right speakers) . I've got a Carver Power amp and Peter Sequerra bookshelf speakers. I played a couple of albums and for about an hour or so I got sound out of both speakers, then the right channel faded and died. 

I wasn't sure if the problem was the Carver or the CJ, so I used a 3.5mm to RCA jack and played my Bose radio with just the Carver and the left and right channel kept going with no fadeout or drop for three I don't think the problem is the power amp, or the speakers. 

I tried the turntable again with the CJ and got sound from both speakers for about fifteen minutes and then the right channel faded out again. Switched cables on the Carver and both speakers worked for a few minutes and then the left speaker dropped out. 

I"m not sure if there's something going on with the CJ right channel output or the Turntable output - I just had them both reconditioned, too!! It's a real head fake because the sound doesn't drop out right away.
As I see it:
- I could try another RCA cable for the CJ to the Carver  and see if that allows the turntable to play both channels for an extended period of time OR=try adding a tuner to the CJ to see if the CJ plays both right and left channels for radio ...that would tell me the CJ is fine and the problem is in the right channel in the turntable somehow. The Linn cartridge, I was told, is fine; however I've also heard-that the cartridge head has right and left channel wiring and maybe that's the issue. 
I haven't had problems with sound in both channels bypassing the CJ and the turntable and playing a radio and an Mp3 with just the Carver.  
I'm open to suggestions.  It's interesting that I got a good two hours with the CJ and the Linn from both speakers when the turntable and the CJ hadn't been used for weeks..  Do I need to put a fan in the stereo cabinet? 

So I guess I"m also looking for advice on a technician in NYC who can check the inside of the CJ and make sure the circuitry isn't blown somewhere.  It just came back from a tube guy so I don't think it's the tubes..
Audio 101: Trouble-shooting. You swapped source, that eliminated the amp. You swapped L/R from the preamp to the amp, redundantly confirming it is not the amp. Now it can only be either the preamp or the turntable.  

Obvious next step: swap phono leads L/R. If the problem stays R then it is indeed the preamp. Then after that if you have to narrow it down to the cartridge or the phono leads you do that by swapping channels on the cart. 

Only after confirming it is the preamp would you move on to swapping tubes L/R. Otherwise it could still be the phono leads, or cartridge. Unlikely, but we don't know. That is why it is so important to progress through and methodically rule out step by step one thing at a time.

"...Do I need to put a fan in the stereo cabinet?..."

Do you have the amp and preamp in a closed cabinet? 
Also if you narrow it down to the preamp the next step is to try and see if it happens with another input. This will narrow it down to the phono stage or the pre-amp section. 

Tubes can go at any time so it does no good to guess and assume, you simply perform each test to methodically narrow it down by a process of elimination.
Avenueb you are having a problem with the Right channel of the CJ.
Something is going south as the unit warms up. If you are uncomfortable with a soldering Iron other than swapping tubes you will need to take it to a tech who has the appropriate equipment to trace it down. There are several things this could be including a bad tube even if they were tested. I am sure the tube fellow did not warm the tube up for 15 minutes before he tested it. 
Fans are cheap insurance..Of course you don't HAVE to do anything.
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Like MC says, keep swapping leads, all the way back to the cartridge itself if necessary, in order to differentiate between a problem in the CJ, phono only or linestage, and then the cartridge and related ICs. Localizing the problem is what you must do first, before anyone outside your listening room can help.

this is a complete shot in the dark, and it is no substitute for doing the work that MC suggested, but I have to wonder about the grip of the wiring on the cartridge pins. If it comes down to that, check those wire clips on the cartridge pins. But first do the homework, is my advice.
Seems a 'heat' issue with a soldered joint or a tube....doesn't occur immediately, but as current flows through it, it warms up and fails.  It's just real slow about it.
A fan likely wouldn't fix it, but can't hurt as a future addition.

Doesn't make sense at the TT or the cart, and the thermodynamics of a stylus would seem a real stretch.

Esoteric gear, esoteric issues....

Good luck, J
"Seems a 'heat' issue with a soldered joint or a tube....doesn't occur immediately, but as current flows through it, it warms up and fails. It's just real slow about it.".... asvjerry

I agree with Jerry perhaps a board trace separating when heated or God only knows some other connection but likely a thermal issue. Good luck and please get back to us once you get it sorted out?